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Migrate from ADF4355 to ADF4356


I have a working design with the ADF4355, and on the followup spin on my board I switched to the ADF4356 thinking it had slightly better performance and was a simple drop in replacement.  Now I am having trouble getting the PLL to lock.  I have done the following.

1.  Created the new configuration register values using the ADF4355 evaluation board software.

2.  Updated the loop filter values based upon the eval board schematics.

Is there anything else that I should be considering?

Thank you in advance.